Primerless adhesive for fiberglass reinforced polyester substrates

ABSTRACT

A two part structural polyurethane adhesive composition and a method of making that adhesive. The adhesive is useful for adhering unprimed fiberglass reinforced polyester substrates and combines an isocyanate terminated prepolymer, and aliphatic polyisocyanate and a curative made of polyol and diamine.

This is a continuation of copending application Ser. No. 07/602,448filed Oct. 10, ,1990 which is a continuation of copending applicationSer. No. 07/376,261 filed Jul. 16, 1989 which is a continuation ofcopending application Ser. No. 07/087,914 filed Aug. 20, 1987 whichissued May 8, 1990 as U.S. Pat. No. 4,876,741.

This invention relates to polyurethane adhesives for bonding fiberglassreinforced polyester substrates which are used in the manufacture of,typically, automobile and marine bodies.

BACKGROUND OF THE INVENTION

Polyurethane structural adhesives have been used for many years inindustry to adhere parts fabricated from fiberglass reinforced polyester(FRP) materials. These materials are also commonly referred to as sheetmolding compound (SMC).

The adhesive bonds must be strong and must maintain their strength bothat elevated temperatures and when exposed to wet environments. Over theyears substantial research effort has been devoted to improving thestrength of these polyurethane structural adhesives. Two patents serveto describe what are, at the present time, typical commerciallyavailable polyurethane structural adhesives. U.S. Pat. No. 3,935,051,"Polyurethane Composition and Laminates Made Therewith", combines aprepolymer component and a curative to make an adhesive for FRP panels.The prepolymer component is the reaction product of polypropylene glycoland toluene diisocyanate. The curative contains polypropylene etherglycol and N, N, N', N'-tetrakis (2-hydroxypropyl) ethylene diamine.Bond strengths were reported to be greater than 60 pounds per squareinch.

U.S. Pat. No. 4,552,934, "Two-Component Adhesive Sage Resistant AtEssentially 1:1 Ratio", describes another two component polyurethaneadhesive also having a prepolymer component and a curative component:This prepolymer is polypropylene ether glycol reacted with aromaticisocyanate and has 3 to 15 percent by weight free isocyanate. Thecurative is polypropylene ether glycol and polypropylene ether triolpartially reacted with some polyarylmethane polyisocyanate before addingpolyamine.

In addition to improvements in the formulations of the adhesivecomponents themselves, a great deal of work has been directed to thedevelopment of primers to be used on FRP substrates to better preparethe substrate for application of the polyurethane adhesive. Primersgenerally are assumed to be absolutely essential elements for stronglybonded laminates.

Bond strength measurements are made both at room temperature and atelevated temperature, that is, at 82° C. Only those adhesives havinghigh bond strengths at 82° C. are considered to be acceptable by theautomotive industry. While adhesives used without primers may pass roomtemperature strength tests, at present only the use of primers providesadequate bond strengths at 82° C.

For example, the General Motors Corporate Specifications for new plasticautomotive substrates require the use of wash primers on test substratesprior to the application of adhesives to these candidate substrates.

A number of representative patents serve to illustrate the efforts madeto improve bond strengths by developing better primers. U.S. Pat. No.3,647,513, "Method for Improving the Adhesion of PolyesterCompositions", teaches the need for a surface treating agent to enhancethe bond strength between adhesives and fiberglass reinforced polyestersubstrates. The surface treating agent or primer recommended is atertiary amine in low-boiling inert organic liquid solvent.

U.S. Pat. No. 3,945,875, "Method For Obtaining Polyester Laminates",teaches the use of a surface treating agent on FRP substrates prior touse of a polyester adhesive. The recommended surface treatment agent isan organic isocyanate containing ethylenic unsaturation. The isocyanateis used in a toluene or methyl ethyl ketone solution.

U.S. Pat. No. 4,004,050, "Two-Part Primer System for FRP Bonding",states that adhesion between a polyurethane adhesive and a polyestersurface is improved by treating the surface with separate applicationsof an organic polyisocyanate and a tertiary amine, each applied insolvent solution to the polyester surface. Methylethyl ketone and thehalogenated hydrocarbon, chlorinated naptha, are recommended solventsfor the surface treatment agents. Practice of this invention requiresthree steps; that is, two surface treatments followed by application ofthe adhesive.

U.S. Pat. No. 4,500,606, "Sealer of Polyester and Method of Use toObtain Laminates", teaches the need for surface treatment of FRPsubstrates with a sealer prior to the use of polyurethane adhesives. Therecommended sealer is a mixture of phenol-formaldehyde resin, polyvinylacetal film former and epoxy resin. This is a typical two step procedurerequiring application of a sealer (or primer) followed by application ofthe adhesive.

Commercially available primers often contain chlorinated hydrocarbonssuch as methylene chloride, a compound under study by the EnvironmentalProtection Agency as being hazardous in the work place. Manufacturersare actively studying ways to minimize or eliminate this and otherharmful solvents from the work environment.

It would be a great improvement over the present technology if thecumbersome two-step process of first applying primer and then applyingadhesive could be streamlined into a one step process in which theprimer step was completely eliminated and the adhesive applied directlyonto the FRP substrate. Elimination of the primer would be a significantadvance not only in the saving of time, but also, in the elimination ofa solvent-exposure opportunity, thus improving the environment for theworkers.

OBJECT OF THE INVENTION

It is therefore an object of this invention to eliminate the use ofprimer on FRP substrates. It is also an object of this invention toprovide a primerless adhesive which retains high bond strength atelevated temperatures. It is a further object of this invention toprovide a primerless adhesive which is stronger at elevated temperaturesthan commercially available primer--requiring adhesives.

BROAD STATEMENT OF THE INVENTION

The present invention is a primerless polyurethane structural adhesivefor fiberglass reinforced polyester (FRP), sheet molding compound (SMC)and other reinforced plastic substrates wherein the adhesive comprisestwo parts: a first part which is a blend of a prepolymer component andan aliphatic isocyanate and a second part which is a curative. Theprepolymer is the reaction product of a polyol and an aromaticisocyanate, the prepolymer product having 3 to 15 percent freeisocyanate groups. The curative part comprises a polyfunctionalpolyether polyol and optionally a catalyst.

In one embodiment the present invention is a method of laminating FRP,SMC and plastic substrates comprising applying an adhesive to a firstunprimed substrate, said adhesive comprising a first part which is ablend of a prepolymer and an aliphatic isocyanate and a second partwhich is a curative and laminating a second unprimed substrate to saidfirst adhesive coated substrate. A final optional heating step mayfollow the laminating step.

In another embodiment the present invention is a laminated substratecomposition comprising a first unprimed FRP, SMC or plastic substratehaving a second unprimed FRP, SMC or plastic substrate adhesively boundto said first substrate by a cured adhesive composition which is thecured residue of an adhesive comprising a first part blend of aprepolymer and an aliphatic isocyanate, said prepolymer comprising thereaction product of a polyol and an aromatic isocyanate and having 3 to15 percent free isocyanate groups and a second part curative comprisinga polyfunctional polyether polyol and optionally a catalyst. Additionaloptional ingredients in the curative are fillers, diamine sag controlagents and pigments.

Advantages of the present invention include the elimination of the useof a primer prior to application of a polyurethane adhesive to FRPsubstrates. Another advantage of this invention is the elimination ofprimer solvent in the workplace. Still a further advantage of thisinvention is the provision of a laminate having bond strengths superiorto those made using conventional primer-requiring adhesives. Yet anotheradvantage, which will become apparent in the Examples, is that the novelprocess provides laminates which are stronger at the 82° C. testtemperature than the bonds made using primer-requiring adhesives. Theseand other advantages of the primerless adhesive of the present inventionwill become readily apparent to those skilled in the art based upon thedisclosure contained herein.

DETAILED DESCRIPTION OF THE INVENTION

This invention, a primerless adhesive, a method of laminating using aprimerless adhesive, and/or a laminated substrate made with a primerlessadhesive has several embodiments.

In one embodiment the primerless adhesive of this invention comprises aprepolymer blended with an aliphatic isocyanate and a curative. Theprepolymer is the reaction product of a polyol and an aromaticisocyanate. The curative comprises a polyfunctional polyether polyol andoptionally a catalyst.

The adhesive of this invention is particularly well adapted for use onfiberglass reinforced polyester substrates. These substrates are madefrom, typically, the reaction product of dipropylene glycol, maleicanhydride, high molecular weight polyvinyl acetate, styrene, peroxidepolymerization initiator and fillers.

The invention is adaptable for use on a variety of other substratesincluding metals, polycarbonates, other plastics such as reactioninjection molding (RIM) polyurethanes, acrylonitrile-butadiene-styrene(ABS) terpolymers, styrene acrylonitrile copolymers (SAN), thermoplasticpolyolefins (TPO) and thermoplastic alloys such aspolycarbonate-polyester blends and polycarbonate-ABS blends. Among theuseful fibers used in reinforcing the substrates are fiberglass,graphite and Kevlar polyamide fiber.

Among the fiberglass reinforced polyester substrates useful in thepractice of this invention are those provided by Diversitech General,Marion, Ind. (GT-7113, GT-8002 and GT-7101 substrates), RockwellInternational Corporation, Centralia, Ill. (RW 9468 Substrate) and BuddCompany, Madison Heights, Mich. (DSM 950 Substrate).

The preferred polyol ingredient of the prepolymer of this invention isdescribed in U.S. Pat. No. 4,552,934 where about 100 parts of an activehydrogen containing material having a molecular weight of 700 to 4500,and preferably from about 1000 to 3500, is reacted with 30 to 120 partsof an organic polyisocyanate as a mixture of aromatic organicpolyisocyanates. Usually, reaction time at elevated temperature ischosen to give a prepolymer in one to several hours. These prepolymersusually have from 3 to 15 percent free isocyanate with 7 to 10 percentfree isocyanate being preferred.

The active hydrogen containing material in the prepolymer component ofthe adhesive may be 700 to 4,000 molecular weight polypropylene oxideether diol, polyethylene oxide polypropylene oxide ether diol,polytetramethylene ether glycol, polyepsilon caprolactone diol,polycarbonate diol, polybutadiene diol or mixtures of these diols. Thepreferred active hydrogen containing material is a polypropylene oxideether diol of 2000 molecular weight.

The second ingredient of the prepolymer component of the adhesive ofthis invention is an aromatic polyisocyanate. Among the useful aromaticpolyisocyanates are: polymethylene polyphenyl isocyanate, 2,4-toluenediisocyanate, 2,4-2,6 (80/20) toluene diisocyanate, 4,4'-diphenylmethanediisocyanate, 1,4-phenylene diisocyanate, 3,3'-dimethoxy -4,4'-biphenyldiisocyanate, 3,3'-dimethyl- 4,4'-biphenyl diisocyanate,3,3'-dimethyl-4,4'-diphenyl methane diisocyanate, or mixtures of thesediisocyanates. One preferred aromatic polyisocyanate is a modifieddiphenyl methane diisocyanate available as Isonate 143L isocyanate fromUpjohn Polymer Chemicals, La Porte, Tex. This modified diphenyl methanediisocyanate contains a high percentage of pure diphenylmethanediisocyanate and a lesser amount of polycarbodiimide adducts.

Also preferred is the polymethylene polyphenyl isocyanate available asMondur MRS isocyanate from Mobay Chemical Corporation, Pittsburgh, Pa.The most preferred aromatic polyisocyanate in the prepolymer of theprimerless adhesive of this invention is a mixture of Isonate 143Lisocyanate and Mondur MRS isocyanate.

Optional ingredients in the prepolymer component of the adhesive of thisinvention include fillers. Representative examples of inert powderyfillers are: aluminum silicates, carbon black, talcs (magnesiumsilicates), calcium carbonate, calcium silicates, barium sulfates,graphite, or mixtures of fillers. The preferred filler ingredient istalc.

Additional optional ingredients in the prepolymer component includecatalysts such as zinc stearate and antioxidants such as Irganox 1010antioxidant available from Ciba Geigy Corporation, Ardsley, N.Y.

The aliphatic isocyanate component of the primerless adhesive of thisinvention is defined herein as any polyfunctional isocyanate havingaliphatic carbon atoms adjacent to the isocyanate groups. Thesealiphatic carbon atoms are thus alpha to the isocyanate groups. Theremay be aromatic functionality elsewhere in the organic isocyanatecompound, but these compounds are referred to herein as aliphaticisocyanates because of the aliphatic nature of the carbon atom alpha tothe isocyanate groups. These alpha carbon atoms may be primary,secondary or tertiary, that, is, either they may have, respectively two,one or no hydrogen atoms; and may be linear or part of a cyclic chain.In addition to the aromatic functionality, the aliphatic isocyanatesused in this invention may contain other functional groups compatiblewith the aliphatic isocyanate, such as unsaturation, ether, mercapto,carbonyl, carboxyl, ester, halogen, etc.

Among the preferred aliphatic polyfunctional isocyanates are:

isophorone diisocyanate (IPDI)

bis (4-isocyanatocyclohexyl) methane (Desmodur W)

m-xylylene diisocyanate (MXDI)

1,3-bis (isocyanatomethyl) cyclohexane (1,3-BIC)

m-tetramethyl xylene diisocyanate (m-TMXDI)

dimethyl-p-isopropenyl benzyl isocyanate (p-TMI)

1,4-cyclohexane diisocyanate (CHDI)

trimethyl hexamethylene diisocyanate (TMHDI)

2-isocyanato ethyl 2,6 diisocyanatohexanoate (T-100)

polyurea derivative of 1,6-hexamethylene diisocyanate--(Desmodur N 3200)

a trimer derivative of 1, 6-hexamethylene diisocyanate (Desmodur N-3300)

low viscosity aliphatic isocyanate (Desmodur KL5-2550)

The more preferred aliphatic isocyanates useful in the primerlessadhesive of this invention are trimethyl hexamethylene diisocyanate(TMXDI), an aliphatic diisocyanate based on a long chain dimerized fattyacid backbone containing 36 carbon atoms, Henkel Corporation, La Grange,Ill. (DDI 1410 diisocyanate), Desmodur N 3200 diisocyanate, isophoronediisocyanate (IPDI) and m-xylylene diisocyanate (MXDI). The mostpreferred aliphatic isocyanate in the practice of this invention ism-xylylene diisocyanate (MXDI). Of course, future developments such ascommercial practicality and availability may affect the selection of thebest adapted aliphatic isocyanate for use in the primerless adhesive. Inthe preferred embodiment of this invention from 0.5 to 6.0 parts byweight isocyanate or mixtures of isocyanates are used with 100 partscombined prepolymer and curative. In the more preferred embodiment ofthis invention from 1 to 4 parts by weight aliphatic isocyanate are usedwith 100 parts combined prepolymer and curative.

The following structures illustrate various aliphatic isocyanates.##STR1##

The curative component of the primerless adhesive of this invention is amixture of active hydrogen containing materials of different molecularweights, a diamine, an optional urethane catalyst and an optionalthickening agent.

The first ingredient of the curative is a polyether polyol having afunctionality of 1.8 to 6.0 and a hydroxyl number from 100 to 1200. Ahydroxyl number range of 200 to 700 and a functionality range of 3 to 5are preferred. Suitable active hydrogen containing materials includediols, triols and tetrols, having primary, secondary and/or tertiaryalcohol groups. Among the preferred polyether polyols are: Pluracol PeP550 polyol, a propoxylated derivative of pentaerythritol having foursecondary hydroxyl groups and a hydroxyl number of 450 available fromBASF Wyandotte Corporation, Parsippany, N.J.; Pluracol P-355 polyol, anethoxylated/propoxylated derivative of ethylene diamine having about 80%of its hydroxyl groups as primary and having a hydroxyl number of 450,also available from BASF Wyandotte Corporation; Thanol R470X polyol,available from Texaco Chemical Co., Bellaire, Tex., a propoxylatedderivative of diethanolamine with a functionality of about 4 and ahydroxyl number of 500; Thanol SF-265 polyol, also available from TexacoChemical Co., a propoxylated derivative of triethanolamine with afunctionality of about 3 and a hydroxyl number of 600; and Dianol 2210polyol, an ethoxylated derivative of bisphenol-A with a functionality of2 and a hydroxyl number of 280, available from Akzo Chemie America,Chicago, Ill.

The second ingredient of the curative component is a diamine. Suitablediamines include: m-phenylene diamine, p-phenylene diamine,4,4'-methylene dianiline, 4,4'-diaminodiphenyl sulfone, piperazine,2,6-diamino-pyridine, p,p'-methylene bis (orthochloroaniline), aminoethyl piperazine, isophoronediamine, diethyltoluene diamine, ethylenediamine, 1, 3 diaminopropane and mixtures of these organic diamines. Thepreferred diamines are piperazine, diethyl toluene diamine (DETDA), andJeffamine D400 diamine, a polyoxypropylene diamine, available fromTexaco Chemical Co., Houston, Tex. From 0.5 to 10.0 parts diamine areused in 100 parts curative.

The third ingredient of the curative component is an optional catalystto facilitate the reaction between active hydrogen containing compoundsand isocyanates. Suitable catalysts include tertiary amines and metalliccatalysts including dibutyltin dilaurate, dibutyltin diacetate, ferricacetyl acetonate, nickel acetylacetonate, dibutyltin dialkyl acid,stannous octoate, dibutyltin diiso-octyl mercapto acetate, and mixturesof these catalysts. The preferred organo metallic catalyst is thedibutyltin dialkyl acid catalyst known as Dabco 125 catalyst availablefrom Air Products, Allentown, Pa. The preferred tertiary amine catalystis 1,4-diazabicyclo octane known as Dabco triethylene diamine catalystalso available from Air Products. Conventional catalytic amounts oforganotin catalyst and tertiary amine catalyst are optionally used inthe curative component. From about 0.1 parts by weight to 3 parts byweight organotin catalyst and from about 0.3 parts by weight to about0.6 parts by weight amine catalyst are optionally used in 100 partsadhesive.

The preferred optional thickening agents are fumed silica available asAerosil 200 fumed silica from Degussa Inc., New York, N.Y.; and Kaofile2 thickener, a surface modified kaolinite (aluminum silicate) fromGeorgia Kaolin Company, Union, N.J.

Small amounts of other optional materials may also be added to thecurative. These include coloring agents, for example, Stantone HCC 6783green coloring agent from Harwick Chemical Company, Akron, Ohio, whichis a blend of C.I. Pigment Green #7 and C.I. Pigment Black #7 dispersedin a polyoxypropylene polyol at 17.8 parts of pigment to 82.2 partspolyol. From 1.5 to 3.0 parts of an aromatic diisocyanate such astoluene diisocyanate may also optionally be included in the curative.The prepolymer and curative are generally used at a ratio of 4 parts byweight prepolymer to 1 part by weight curative. Thus, in a preferredembodiment of this primerless adhesive, there are 70 to 85 partsprepolymer, 0.5 to 6.0 parts aliphatic isocyanate and the remaindercurative.

In practicing the process of the present invention the prepolymer isfirst prepared by reacting the excess aromatic polyisocyanate withpolyol. Next the aliphatic isocyanate is blended with the prepolymer.This prepolymer blend is provided to the customer as one part of a twopack system. The curative component is provided in the other part of thetwo pack system. The customer combines the prepolymer blend pack withthe curative pack in the desired ratio, usually 4 weight partsprepolymer is blended with 1 weight part curative. A static mixer may beused. The adhesive is applied to the first substrate by conventionalmeans. The second substrate is then laminated over the first adhesivecoated substrate. The adhesive is cured either at room temperature or byheating to 135° C. for 30 minutes.

The nature and advantage of this invention can be more readily seen andappreciated by reference to the following representative examples whereall parts and percentages are by weight unless otherwise indicated.Also, all references cited herein are expressly incorporated herein byreference.

EXAMPLE 1

This Example 1 describes the preparation of a typical prepolymercomponent of the primerless adhesive of this invention. A prepolymer wasmade by adding, with a nitrogen purge, 100 parts of polypropylene oxideether diol of 2000 molecular weight (Olin Poly-G 20-56 polyol, OlinChemicals, Stamford, Conn.) followed by 54.4 parts dry Mistron RCS talc(Cyprus Industrial Minerals Company, Los Angeles, Calif.) with stirringand heating at 100° to 110° C. The wetted mix was sheared at high speedfor 30 minutes. The temperature was then stabilized at 60° C. followedby one hour of vacuum heating at 26 inches mercury (30 inches mercurybeing full vacuum on the production gauge). Then, a mixture of 30.9parts of Mondur MRS isocyanate and 54.2 parts of Isonate 143L isocyanatewas added. The components were allowed to react under vacuum at 80°-90°C. until the isocyanate content reached the theoretical value of 8.6%. Alast component, 0.43 parts of zinc stearate, was then added. After aboutten minutes of mixing the prepolymer was discharged. The finishedproduct was transferred to a bucket and sealed under a nitrogenatmosphere. The viscosity was 27,000±5000 centipoise at 25° C.

EXAMPLE 2

This Example 2 describes the preparation of a curative component usefulin the primerless adhesive of this invention. A curative was prepared bycharging 34.9 parts Pluracol PeP 550 polyether tetrol of 500 molecularweight (BASF Wyandotte Corporation, Parsippany, N.J.) and 18.8 partsPluracol 355 polyether tetrol of 500 molecular weight (BASF WyandotteCorporation) to a reactor fitted with a lid, stirrer and degassingoutlet.

The polyols were heated to 100°-110° C. with stirring. Toluenediisocyanate in the amount of 1.3 parts, 3.5 parts Aerosil fumed silicathickening agent (Degussa Inc., New York, N.Y.), and 0.27 parts StantoneHCC 6783 green coloring agent were added sequentially; allowing time foreach material to be dispersed uniformly in the mix. The mixture wasdegassed at 3 mm mercury for two hours. Anhydrous piperazine in theamount of 1.0 part (Texaco Chemical Co., Houston, Tex.) andtriethylenediamine catalyst in the amount of 0.27 parts were added. Thetemperature was adjusted to 80° C. and the product was degassed for anadditional 12 minutes. The curative component of the primerless adhesiveof this invention had a viscosity of 10,000±1,500 centipoise at 25° C.

EXAMPLE 3

The following comparative Example 3 illustrates the use of a commercialadhesive on FRP substrates without the use of a primer.

Three inch by one inch pieces of Diversitech General GT-7113 FRPsubstrate were wiped clean with a paper tissue moistened with a 10%solution of isopropanol in water. Lap shear samples having bonded areasof 1"×1"×0.030" were prepared by blending the prepolymer of Example 1with the curative of Example 2 in a prepolymer: curative weight ratio of4.0:1.0 (Equivalents curative/equivalents prepolymer of 0.91). Sampleswere postcured at 135° C. for one hour. Samples were conditioned in anoven at 82° C. for 15 minutes before testing on an Instron machine at0.5"/min. crosshead speed (ASTM method D1002). The results are reportedin Table 1. When the sample breaks cleanly between the adhesive layerand the substrate without any tearing or delamination of the FRPsubstrate the result is recorded as "no good" or "NG". When the samplepiece breaks perpendicular to the edge of the adhesive the result isrecorded as substrate failure "SF".

                  TABLE 1                                                         ______________________________________                                        Adhesion of Commercial Adhesive to Unprimed FRP                               [Prepolymer of Example 1 and Curative of Example 2]                           Lap Shear at 82° C., psi (% DL)                                        ______________________________________                                        C4644-4-25     150 (NG)                                                                      140 (NG)                                                                      40 (NG)                                                                       70 (NG)                                                        C4557-194-13   100 (NG)                                                                      10 (NG)                                                                       60 (NG)                                                        average        82 (NG)                                                        ______________________________________                                    

These results should be compared with those attained when the commercialFRP adhesive is used along with a commercial primer as described inExample 4 following.

EXAMPLE 4

In Comparative Example 4 the Example 1 prepolymer is blended with theExample 2 curative and applied to a substrate which has been previouslytreated with a commercially available primer. Following the procedure ofExample 3, pieces of different grades of FRP substrates, GT 7113, GT7101, RW 9468 and GT 8002, were treated with the commercially availablePLIOGRIP 6036 primer (Ashland Chemical Co., Columbus, Ohio). Theprepolymer of Example 1 and the curative of Example 2 were blended in aprepolymer: curative weight ratio of 4.0:1.0 and applied as described inExample 3. This is a equivalents curative: prepolymer equivalent ratioof 0.9:1.0. Samples were postcured at 135° C. for one hour andconditioned at 82° C. for 15 minutes before testing as described inExample 3. The portion of the area of the 1"×1" surface of the breakwhich is torn FRP substrate is reported as percent delamination, thatis, where 25% of the surface is torn substrate and 75% of the surface ofthe break is adhesive the result is "25% delamination (DL)", where 75%of the surface of the break is torn substrate and 25% of the surface isadhesive the result is "75% delamination". The desired result is highbond strength with a high percent delamination. The results are reportedin Table 2.

                  TABLE 2                                                         ______________________________________                                        ADHESION OF FOUR FRP SUBSTRATES                                               TO STANDARD COMMERCIAL ADHESIVE                                               USING COMMERCIAL PRIMER                                                       Lap Shear, psi (% DL)                                                         measured at 82° C.                                                     7113       7101       9468       8002                                         ______________________________________                                        380 (80%)  570 (90%)  440 (30%   430 (70%)                                    380 (45%)  470 (80%)  290 (98%)  360 (95%)                                    350 (100%) 490 (95%)  330 (75%)  390 (95%)                                    530 (100%)                                                                    450 (95%)                                                                     410 (95%)                                                                     460 (99%)                                                                     450 (100%)                                                                    480 (75%)                                                                     432 (86%)  510 (88%)  353 (68%)  393 (87%)                                    average    average    average    average                                      ______________________________________                                    

Comparison of the results in Table 1 and Table 2 shows that thecommercial adhesive used without primer provides only a fraction of thebond strength achieved using primer. No substrate delamination occurs inthe absence of primer. Use of commercial adhesive with primer providessubstantial bond strengths and from 68 to 88% delamination.

EXAMPLE 5

This Example 5 illustrates the use of various aliphatic isocyanates toprovide the primerless adhesive of this invention.

A number of aliphatic isocyanates were evaluated at 4.0% levels in theadhesive by adding 1.25 grams isocyanate to 24.0 grams of the prepolymerof Example 1. The curative of Example 2 in the amount of 6.0 grams wasadded and mixed for one minute. Samples were prepared as described inExample 3 and postcured at 135° C. for one hour. The following aliphaticisocyanates were used:

isophorone diisocyanate (IPDI)

bis (4-isocyanatocyclohexyl) methane (Desmodur W)

meta-xylylene diisocyanate (MXDI)

1,3 - bis (isocyanatomethyl) cyclohexane (1,3-BIC)

m-tetramethyl xylenediisocyanate (m-TMXDI)

dimethyl-p-isopropenyl benzyl isocyanate (p-TMI)

trimethyl hexamethylene diisocyanate (TMHDI)

2-isocyanatoethyl 2,6 diisocyanatohexanoate (T-100 Toray Industries,Inc., Tokyo, Japan)

a low viscosity aliphatic polyisocyanate from Mobay Chemical Corp.(Desmodur KL5-2550)

1,6-hexamethylene diisocyanate (HDI)

The ratio of equivalents of curative/prepolymer was 0.91. Theequivalents of curative/prepolymer plus aliphatic isocyanate are statedin Table 3.

                                      TABLE 3                                     __________________________________________________________________________                120-3                                                                             120-8                                                                             120-9                                                                             120-10                                                                             120-11                                                                              120-12                                                                            120-13                                                                             120-14                                                                            120-15                                                                             129-14                   __________________________________________________________________________    Aliph NCO   IPDI                                                                              Des W                                                                             MXDI                                                                              1,3-BIC                                                                            m-TMXDI                                                                             p-TMI                                                                             TMHDI                                                                              T-100                                                                             KL5-2550                                                                           HDI                      Eq Curative/                                                                              0.74                                                                              0.76                                                                              0.72                                                                              0.72 0.75  0.81                                                                              0.73 0.71                                                                              0.80 0.70                     Eq Prepolymer +                                                               Aliphatic NCO                                                                 Lap Shear, psi (% DL)                                                                     400 450 380 350  290   210 310  430 490  330                      at 82° C.                                                                          (20%)                                                                             (NG)                                                                              (100%)                                                                            (NG) (NG)  (SF)                                                                              (NG) (100%)                                                                            (100%)                                                                             (100%)                               390 430 380 440  300   340 360  360 425  270                                  (NG)                                                                              (50%)                                                                             (100%)                                                                            (90%)                                                                              (NG)  (NG)                                                                              (NG) (100%)                                                                            (100%)                                                                             (NG)                                 500 410 400 440  340   290 450  450 410  330                                  (90%)                                                                             (NG)                                                                               (85%)                                                                            (90%)                                                                              (NG)  (NG)                                                                              (NG)  (98%)                                                                             (97%)                                                                             (NG)                                 420 350 370 510  370   320 490  480 370  320                                  (65%)                                                                             (NG)                                                                               (75%)                                                                            (85%)                                                                              (NG)  (NG)                                                                              (95%)                                                                               (98%)                                                                             (97%)                                                                             (NG)                     __________________________________________________________________________

Review of Table 3 shows bond strength results with all of the aliphaticisocyanates providing superior strengths to the Table 1 strengths wherethe commercial adhesive was also used without a primer. In additionseveral of the aliphatic isocyanates gave bonds which, on breaking,showed significant substrate delamination.

EXAMPLE 6

This Example 6 illustrates the effect of variation of lowering the ratioof the equivalents of curative to equivalents of prepolymer from 0.91 to0.80 or 0.70 (curative level).

Different concentrations of isophorone diisocyanate (IPDI) were preparedas described in Example 5 at different curative levels using theprepolymer of Example 1 and the curative of Example 2. The results arereported in Table 4.

                                      TABLE 4                                     __________________________________________________________________________                  125-1 125-2 125-3 125-4 125-5 125-6                             __________________________________________________________________________    Prepolymer, g 24.0  24.0  24.0  24.0  24.0  24.0                              IPDI, g       0.30  0.60  0.90  0.30  0.60  0.90                              C ive, g      4.60  4.60  4.60  5.26  5.26  5.26                              Eq. curative/prepolymer                                                                     0.70  0.70  0.70  0.80  0.80  0.80                              Eq. curative/prepolymer +                                                                   0.66  0.63  0.60  0.76  0.72  0.68                              IPDI                                                                          Wt. % IPDI    1.0   2.0   3.0   1.0   2.0   3.0                               Lap Shear, psi (% DL)                                                                       440 (95%)                                                                           440 (100%)                                                                          460 (100%)                                                                          430 (90%)                                                                           500 (80%)                                                                           425 (98%)                         at 82° C.                                                                            470 (70%)                                                                           400 (90%)                                                                           390 (100%)                                                                          470 (97%)                                                                           490 (100%)                                                                          440 (100%)                                      430 (95%)                                                                           420 (100%)                                                                          450 (100%)                                                                          380 (95%)                                                                           430 (100%)                                                                          420 (100%)                                      470 (95%)                                                                           440 (90%)                                                                           500 (100%)                                                                          475 (95%)                                                                           460 (90%)                                                                           420 (90%)                         __________________________________________________________________________

EXAMPLE 7

This Example 7 reports the study of additional aliphatic isocyanates atvarious curative levels and isocyanate levels.

The results of blending the following aliphatic isocyanates with theprepolymer of Example 1 and then adding the curative of Example 2 arereported in the following Tables:

meta-xylylenediisocyanate, MXDI; Table 5

2-isocyanatoethyl 2,6 diisocyanatohexanoate, Toray T-100; Table 6

Desmodur KL5-2550; Table 7

1,3-bis(isocyanato methyl) cyclohexane, 1,3-BIC; Table 8

                                      TABLE 5                                     __________________________________________________________________________                     125-21                                                                            125-22                                                                             125-23 125-24                                                                            125-25                                                                            125-26                                                                            125-27                                                                            125-28                       __________________________________________________________________________    Prepolymer, g    24.0                                                                              24.0 24.0   24.0                                                                              24.0                                                                              24.0                                                                              24.0                                                                              24.0                         MXDI, g          0.30                                                                              0.60 0.90   1.25                                                                              0.30                                                                              0.60                                                                              0.90                                                                              1.20                         Curative, g      6.0 6.0  6.0    6.0 4.60                                                                              4.60                                                                              4.60                                                                              4.60                         Eq. curative/prepolymer                                                                        0.91                                                                              0.91 0.91   0.91                                                                              0.70                                                                              0.70                                                                              0.70                                                                              0.70                         Eq. curative/prepolymer + MXDI                                                                 0.86                                                                              0.81 0.76   0.72                                                                              0.66                                                                              0.62                                                                              0.58                                                                              0.55                         Wt. %/MXDI       1.0 2.0  3.0    4.0 1.0 2.0 3.0 4.0                          Lap Shear, psi (% DL)                                                                          430 470  330    470 500 450 440 560                          at 82° C. (95%)                                                                             (100%)                                                                              (60%)*                                                                               (98%)                                                                            (100%)                                                                             (80%)                                                                            (100%)                                                                            (100%)                                        410 440  295    400 460 350 350 510                                           (60%)                                                                             (97%)                                                                               (25%)**                                                                             (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                             (95%)                                        430 460  370    460 450 420 380 430                                           (80%)                                                                             (97%)                                                                                (10%)***                                                                           (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                        420 500  470    560 340 360 420 460                                           (75%)                                                                             (65%)                                                                              (80%)  (98%)                                                                             (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                       __________________________________________________________________________     *40% Substrate Failure (SF)                                                   **70% SF                                                                      ***90% SF                                                                

                                      TABLE 6                                     __________________________________________________________________________                    125-31                                                                            125-32                                                                            125-33                                                                            125-34                                                                            125-35                                                                            125-36                                                                            125-37                                                                            125-38                            __________________________________________________________________________    Prepolymer, g   24.0                                                                              24.0                                                                              24.0                                                                              24.0                                                                              24.0                                                                              24.0                                                                              24.0                                                                              24.0                              Toray T-100, g  0.30                                                                              0.60                                                                              0.90                                                                              1.25                                                                              0.30                                                                              0.60                                                                              0.90                                                                              1.20                              Curative, g     6.0 6.0 6.0 6.0 4.60                                                                              4.60                                                                              4.60                                                                              4.60                              Eq curative/prepolymer                                                                        0.91                                                                              0.91                                                                              0.91                                                                              0.91                                                                              0.70                                                                              0.70                                                                              0.70                                                                              0.70                              Eq curative/prepolymer + T-100                                                                0.85                                                                              0.80                                                                              0.76                                                                              0.71                                                                              0.65                                                                              0.61                                                                              0.58                                                                              0.55                              Wt % T-1000     1.0 2.0 3.0 4.0 1.0 2.0 3.0 4.0                               Lap Shear, psi (% DL)                                                                         470 400 530 500 430 490 480 470                               at 82° C.                                                                              (90%)                                                                             (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                            430 470 520 450 440 440 540 440                                               (97%)                                                                             (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                            460 480 440 470 520 410 520 380                                               (90%)                                                                             (100%)                                                                            (100%)                                                                             (98%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                            510 510 510 310 510 450 550 500                                               (90%)                                                                             (100%)                                                                             (90%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                                                                            (100%)                            __________________________________________________________________________

                                      TABLE 7                                     __________________________________________________________________________                      128-5                                                                             128-6                                                                             128-7                                                                              128-8                                                                             128-9                                                                             128-10                                                                            128-11                                                                             128-12                        __________________________________________________________________________    Prepolymer, g     24.0                                                                              24.0                                                                              24.0 24.0                                                                              24.0                                                                              24.0                                                                              24.0 24.0                          KL 5-2550, g      0.30                                                                              0.60                                                                              0.90 1.25                                                                              0.30                                                                              0.60                                                                              0.90 1.20                          Curative, g       6.0 6.0 6.0  6.0 4.60                                                                              4.60                                                                              4.60 4.60                          Eq curative/prepolymer                                                                          0.91                                                                              0.91                                                                              0.91 0.91                                                                              0.70                                                                              0.70                                                                              0.70 0.70                          Eq curative/prepolymer + KL52550                                                                0.88                                                                              0.86                                                                              0.83 0.80                                                                              0.68                                                                              0.66                                                                              0.64 0.62                          Wt % KL 5-2550    1.0 2.0 3.0  4.0 1.0 2.0 3.0  4.0                           Lap Shear, psi (% DL)                                                                           400 430 410  460 510 520 450  470                           at 82° C.  (NG)                                                                               (5%)                                                                             (NG)  (98%)                                                                            (100%)                                                                             (95%)                                                                            (100%)                                                                             (95%)                                           390 390 520  420 580 490 430  410                                             (50%)                                                                             (98%)                                                                             (50%)                                                                              (100%)                                                                            (100%)                                                                            (100%)                                                                            (90%)                                                                              (80%)                                           430 410 500  420 470 460 490  400                                             (90%)                                                                             (98%)                                                                             (50%)                                                                               (98%)                                                                             (97%)                                                                            (100%)                                                                            (90%)                                                                              (90%)                                           400 420 540  400 470 430 330  400                                             (90%)                                                                             (98%)                                                                             (100%)                                                                             (100%)                                                                            (100%)                                                                            (SF)                                                                              (SF) (95%)                         __________________________________________________________________________

                                      TABLE 8                                     __________________________________________________________________________                     129-1                                                                             129-2                                                                              129-3                                                                              129-4                                                                              129-5                                                                             129-6                                                                              129-7                                                                             129-8                        __________________________________________________________________________    Prepolymer, g    24.0                                                                              24.0 24.0 24.0 24.0                                                                              24.0 24.0                                                                              24.0                         1,3-BIC, g       0.30                                                                              0.60 0.90 1.25 0.30                                                                              0.60 0.90                                                                              1.20                         Curative, g      6.0 6.0  6.0  6.0  4.60                                                                              4.60 4.60                                                                              4.60                         Eq curative/prepolymer                                                                         0.91                                                                              0.91 0.91 0.91 0.70                                                                              0.70 0.70                                                                              0.70                         Eq curative/prepolymer + 1,3-BIC                                                               0.86                                                                              0.81 0.77 0.72 0.66                                                                              0.62 0.59                                                                              0.56                         Wt % 1,3-BIC     1.0 2.0  3.0  4.0  1.0 2.0  3.0 4.0                          Lap Shear, psi (% DL)                                                                          320 470  460  440  510 230  390 110                          at 82° C. (40%)                                                                             (98%)                                                                              (98%)                                                                              (100%)                                                                             (100%)                                                                            (NG) (80%)                                                                             (NG)                                          430 470  430  520  440 450  460 210                                           (90%)                                                                             (98%)                                                                              (75%)                                                                              (98%)                                                                               (60%)                                                                            (100%)                                                                             (80%)                                                                             (NG)                                          450 460  450  560  400 460  420  20                                           (50%)                                                                             (95%)                                                                              (98%)                                                                              (98%)                                                                              (100%)                                                                            (90%)                                                                              (95%)                                                                             (NG)                                          430 470  420  560  420 500  130 120                                           (20%)                                                                             (100%)                                                                             (100%)                                                                             (98%)                                                                              (100%)                                                                            (90%)                                                                              (NG)                                                                              (NG)                         __________________________________________________________________________

EXAMPLE 8

This Example 8 illustrates use of the aliphatic isocyanates of theprimerless adhesive of this invention using a different prepolymer and adifferent curative from those of Example 1 and Example 2 previouslyused.

Following the procedures of Example 1 a different prepolymer was madeusing 100.0 g Terathane 2000 polyol, a polytetramethylene ether glycolavailable from DuPont having a molecular weight of 2000, 46.6 g MistronRCS talc, 1.0 g Irganox 1010 antioxidant available from Ciba GeigyCorporation, and 85.1 g Isonate 143L modified diphenyl methanediisocyanate. This prepolymer had an isocyanate content of 8.7%.Aliphatic isocyanates: isophorone diisocyanate (IPDI), meta-xylylenediisocyanate (MXDI), 2-isocyanato ethyl 2,6 diisocyanato hexanoate(T-100) and Desmodur KL 5-2550 aliphatic isocyanate were each separatelyadded to and blended with this prepolymer before adding a new curativemade according to the procedure of Example 2 using the following: 95.9 gThanol SF-265 polyol, 101.5 g Dianol 2210 polyol, 22.3 g diethyltoluenediamine and 54.9 g Kaofile-2 thickener.

The aliphatic isocyanates were added in the amounts shown to 25.0 gprepolymer and this blend added to 6.10 g curative. The equivalentcurative/prepolymer ratio was 0.75.

Samples were postcured at 135° C. for one hour. Results of the lap shearadhesion tests at 82° C. are summarized in Table 9.

                                      TABLE 9                                     __________________________________________________________________________                  126-1                                                                             126-2                                                                              126-3                                                                             126-4                                                                             126-5                                                                             126-6                                                                              126-7                                 __________________________________________________________________________    IPDI, g       0.31                                                                              0.64                                                        MXDI, g                0.31                                                                              0.64                                               T-100, g                       0.31                                                                              0.64                                       KL 5-2550, g                            0.31                                  Eq curative/prepolymer plus                                                                 0.71                                                                              0.67 0.70                                                                              0.66                                                                              0.70                                                                              0.66 0.73                                  aliph NCO                                                                     Wt. % Aliph Isocyanate                                                                      1.0 2.0  1.0 2.0 1.0 2.0  1.0                                   Lap Shear, psi (% DL)                                                                       390 430  420 370 450 470  470                                   at 82° C.                                                                             (98%)                                                                            (95%)                                                                              (100%)                                                                             (65%)                                                                            (50%)                                                                             (95%)                                                                              (100%)                                              460 480  490 420 410 480  460                                                 (100%)                                                                            (95%)                                                                               (93%)                                                                            (100%)                                                                            (NG)                                                                              (98%)                                                                              (100%)                                              440 410  440 360 450 450  440                                                  (98%)                                                                            (100%)                                                                             (100%)                                                                            (100%)                                                                            (85%)                                                                             (100%)                                                                             (100%)                                              410 540  390 460 440 420  390                                                 (100%)                                                                            (90%)                                                                              (100%)                                                                            (100%)                                                                            (97%)                                                                             (95%)                                                                               (97%)                                __________________________________________________________________________

EXAMPLE 9

In this following Example 9 a different curative was used with theprepolymer of Example 8 and each of the aliphatic isocyanates;isophorone diisocyanate (IPDI) meta-xylylene diisocyanate (MXDI) and2-isocyantoethyl 2,6 diisocyanato hexanoate (T-100) was evaluated.

Another curative was prepared by combining, according to the procedureof Example 2, 90.0 g Thanol R470X polyol, 91.5 g Pluracol P-355 polyol,22.3 g diethyl toluene diamine (DETDA) and 5.2 g Aerosil 200 fumedsilica thickening agent. Different amounts of aliphatic isocyanate asshown on Table 10 were added to 25.0 g. of the Example 8 prepolymer andthen 4.62 grams of this Example 9 curative were added. The equivalentratio of curative/prepolymer was 0.75. The substrate was DiversitechGeneral GT-7113 FRP. Postcure was one hour at 135° C. Lap shear adhesiontests are summarized in Table 10.

                                      TABLE 10                                    __________________________________________________________________________                        126-9 126-11                                                                              126-13                                                                              126-14                                  __________________________________________________________________________    IPDI, g             0.30                                                      MXDI, g                   0.30                                                T-100, g                        0.30  0.60                                    Eq. curative/prepolymer plus Aliph NCO                                                            0.71  0.70  0.70  0.66                                    Wt. % Aliph Isocyanate                                                                            1.0   1.0   1.0   2.0                                     Lap Shear, psi (% DL)                                                                             440 (98%)                                                                           470 (98%)                                                                           450 (100%)                                                                          500 (100%)                              at 82° C.    450 (100%)                                                                          440 (100%)                                                                          460 (100%)                                                                          490 (100%)                                                  440 (98%)                                                                           460 (95%)                                                                           450 (100%)                                                                          520 (70%)                                                   440 (100%)                                                                          510 (100%)                                                                          410 (100%)                                                                          450 (100%)                              __________________________________________________________________________

EXAMPLE 10

This Example 10 illustrates the use of the most preferred aliphaticisocyanate in the primerless adhesive of this invention; an alternativecurative is used. The prepolymer of Example 1 is blended with m-xylylenediisocyanate (MXDI) and then mixed with the new curative of Example 10.

Following the procedure of Example 2, Pluracol PeP 550 polyether tetrolin the amount of 34.89 grams, Pluracol P-355 polyol in the amount of18.79 grams, Jeffamine D400 polymeric aliphatic diamine in the amount of4.60 grams, triethylene diamine catalyst in the amount of 0.27 grams,8.68 g Kaofile 2 filler and 0.27 g Stantone 6783 green coloring agentwere combined. The theoretical hydroxyl number of this curative was376.5. Following the test procedures of Example 3 different ratios ofprepolymer/curative were evaluated. The substrate was GT-7113 FRP. Theresults are reported in Table 11.

                                      TABLE 11                                    __________________________________________________________________________                      142-2                                                                              142-3  142-4  142-5  142-6                             __________________________________________________________________________    Prepolymer/MXDI at 24.0/0.90, g                                                                 24.90                                                                              24.90  24.90  24.90  24.90                             Curative, g       7.85 6.75   6.23   5.64   5.09                              Eq. Curative/Prepolymer                                                                         1.06 0.91   0.84   0.76   0.69                              Eq. Curative/Prepolymer + MXDI                                                                  0.89 0.77   0.71   0.64   0.58                              Wt. % MXDI        2.7  2.8    2.9    2.9    3.0                               Lap Shear, psi (% DL)                                                                           120 (NG)                                                                           500 (80%)                                                                             410 (100%)                                                                          440 (80%)                                                                            320 (SF).sup.                     at 82° C.   70 (NG)                                                                           480 (98%)                                                                            320 (98%)                                                                            330 (98%)                                                                            440 (100%)                                               510 (98%)                                                                            380 (95%)                                                                             430 (100%)                                                                          370 (98%)                                                 430 (100%)                                                                          390 (80%)                                                                            440 (98%)                                                                            90 (NG).sup.                      __________________________________________________________________________

EXAMPLE 11

This Example 11 illustrates results obtained when various additionalaliphatic isocyanates were used in the primerless adhesive of thisinvention.

Following the procedure of Example 3 the following aliphatic isocyanateswere added to the prepolymer of Example 1 and mixed with the curative ofExample 2. The GT-7113 FRP substrate was used. The results are reportedin the indicated tables.

Trimethylhexamethylene diisocyanate TMHDI--Table 12

1,6 Hexamethylene diisocyanate, HDI-Table 13

A diisocyanate based on a long chain, dimerized fatty acid backbonecontaining 36 carbon atoms, DDI 1410--Table 14

A polyurea derivative of 1,6-hexamethylene diisocyanate, DesmodurN-3200--Table 15

                                      TABLE 12                                    __________________________________________________________________________                      146-6 146-7 146-8 146-9 146-10                              __________________________________________________________________________    Prepolymer/TMHDI at 24.00/1.23, g                                                               25.23 25.23 25.23 25.23 25.23                               Curative, g       6.58  5.99  5.39  5.00  4.61                                Eq. Curative/Prepolymer                                                                         1.00  0.91  0.82  0.76  0.70                                Eq. Curative/Prepolymer + TMHDI                                                                 0.81  0.73  0.66  0.61  0.57                                Wt. % MXDI        3.9   3.9   4.0   4.1   4.1                                 Lap Shear, psi (% DL)                                                                           440 (98%)                                                                           410 (98%)                                                                           470 (100%)                                                                          510 (95%)                                                                           410 (NG).sup.                       at 82° C.  450 (95%)                                                                           440 (90%)                                                                           430 (SF).sup.                                                                       430 (93%)                                                                           410 (100%)                                            430 (90%)                                                                           400 (40%)                                                                           200 (NG).sup.                                                                       340 (90%)                                                                           500 (98%)                                             450 (95%)                                                                           440 (60%)                                                                           440 (100%)                                                                          310 (90%)                                                                           400 (100%)                          __________________________________________________________________________

                                      TABLE 13                                    __________________________________________________________________________                  129-11                                                                             129-12                                                                              129-13 129-14                                                                              129-15 129-16                                                                              129-17                                                                             129-18                __________________________________________________________________________    Prepolymer    24.0 24.0  24.0   24.0  24.0   24.0  24.0 24.0                  HDI,          0.30 0.60  0.90   1.25  0.30   0.60  0.90 1.20                  Curative      6.0  6.0   6.0    6.0   4.60   4.60  4.60 4.60                  Eq. Curative/Prepolymer                                                                     0.91 0.91  0.91   0.91  0.70   0.70  0.70 0.70                  Eq. Curative/ 0.85 0.80  0.75   0.70  0.65   0.61  0.57 0.54                  (Prepolymer + HDI)                                                            Wt. % HDI     1.0  2.0   3.0    4.0   1.0    2.0   3.0  4.0                   Lap Shear, psi (% DL)                                                                       390 (NG)                                                                           410 (85%)                                                                           400 (65%)                                                                             330 (98%)                                                                          350 (65%)                                                                             450 (95%)                                                                          120 (NG)                                                                           230 (NG)              at 82° C.                                                                            420 (NG)                                                                           390 (NG)                                                                            360 (NG)                                                                             270 (NG)                                                                            510 (85%)                                                                            110 (NG)                                                                             10 (NG)                                                                           350 (NG)                                 430 (90%)                                                                            420 (100%)                                                                          330 (NG)                                                                            450 (98%)                                                                            150 (NG)    490 (70%)                               430 (80%)                                                                           460 (90%)                                                                            320 (NG)                                                                             420 (100%)                                                                           530 (85%) .sup.  450            __________________________________________________________________________                                                            (100%)            

                                      TABLE 14                                    __________________________________________________________________________                      153-1 153-2 153-3 153-4  153-5 153-6                        __________________________________________________________________________    Prepolymer, g     24.0  24.0  24.0  24.0   24.0  24.0                         DDI 1410, g       0.30  0.60  0.90  0.30   0.60  0.90                         Curative, g       6.00  6.00  6.00  4.60   4.60  4.60                         Eq. Curative/Prepolymer                                                                         0.91  0.91  0.91  0.70   0.70  0.70                         Eq. Curative/(Prepolymer + DDI)                                                                 0.89  0.88  0.86  0.68   0.67  0.66                         Wt. % DDI         1.0   2.0   3.0   1.0    2.0   3.0                          Lap Shear, psi (% DL)                                                                           440 (10%)                                                                           380 (50%)                                                                           440 (15%)                                                                           570 (98%)                                                                            440 (100%)                                                                          430 (100%)                   82° C.     500 (85%)                                                                           400 (98%)                                                                           380 (85%)                                                                           440 (70%)                                                                            520 (90%)                                                                           460 (100%)                                     440 (85%)                                                                           400 (90%)                                                                           410 (90%)                                                                           460 (95%)                                                                            460 (95%)                                                                           560 (100%)                                     430 (90%)                                                                           360 (70%)                                                                           360 (NG)                                                                             500 (100%)                                                                          510 (100%)                         __________________________________________________________________________

                                      TABLE 15                                    __________________________________________________________________________                      148-1 148-2 148-3  148-4 148-5 148-6                        __________________________________________________________________________    Prepolymer, g     24.0  24.0  24.0   24.0  24.0  24.0                         Desmodur N-3200, g                                                                              0.30  0.60  0.90   1.25  0.30  0.60                         Curative, g       6.00  6.00  6.00   6.00  4.60  4.60                         Eq. Curative/Prepolymer                                                                         0.91  0.91  0.91   0.91  0.70  0.70                         Eq. Curative/(Prepolymer + N3200)                                                               0.88  0.85  0.83   0.80  0.68  0.65                         Wt. % N-3200      1.0   2.0   3.0    4.0   1.0   2.0                          Lap Shear, psi (% DL)                                                                           400 (90%)                                                                           510 (100%)                                                                          450 (95%)                                                                            430 (100%)                                                                          470 (100%)                                                                          380 (100%)                   82° C.     420 (55%)                                                                           400 (100%)                                                                           410 (100%)                                                                          440 (100%)                                                                          460 (100%)                                                                          390 (100%)                                     430 (85%)                                                                           420 (100%)                                                                          400 (95%)                                                                            530 (98%)                                                                           390 (100%)                                                                          480 (100%)                                     440 (85%)                                                                           470 (90%)                                                                           390 (10%)                                                                            520 (95%)                                                                           410 (100%)                                                                          490 (100%)                   __________________________________________________________________________

We claim:
 1. A two part structural polyurethane adhesive composition useful for adhering a first unprimed fiber reinforced polyester substrate to a second unprimed substrate comprising a blend of aa) prepolymer component comprising the reaction product of a polyol and an aromatic polyisocyanate, said prepolymer component having 3 to 15 percent free isocyanate groups, b) an aliphatic polyisocyanate, and c) a curative component comprising a polyfunctional polyether polyol and a diamine.
 2. The adhesive of claim 1 wherein said aliphatic polyisocyanate has an aliphatic carbon alpha to said isocyanate group wherein said alpha carbons are --CH₂ R, --CHRR' or --CR'R", where R, R' and R" are independently substituted or unsubstituted aromatic groups or substituted or unsubstituted aliphatic groups of six to forty carbon atoms.
 3. The adhesive of claim 2 wherein said aliphatic isocyanate has a molecular weight from 120 to
 700. 4. The adhesive of claim 3 wherein said aliphatic isocyanate is selected from the group consisting of isophorone diisocyanate, bis- (4-isocyanatocyclohexyl) methane, m-xylylenediisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, m-tetramethylxylene diisocyanate, dimethyl-p-isopropenyl benzyl isocyanate, trimethyl hexamethylene diisocyanate, 2-isocyanatoethyl 2, 6 diisocyanatohexanoate, hexamethylene diisocyanate and mixtures thereof.
 5. The adhesive of claim 4 wherein said primerless adhesive comprises about 100 weight parts combined prepolymer and curative and from 0.5 to 6.0 weight parts aliphatic isocyanate.
 6. The adhesive of claim 5 wherein said primerless adhesive comprises from 50 to 85 weight parts prepolymer, from 0.5 to 6.0 weight parts aliphatic isocyanate, and the balance curative to make 100 parts.
 7. The adhesive of claim 6 wherein said primerless adhesive comprises about 80 parts prepolymer, about 20 parts curative and from 0.5 to 4.0 parts m-xylylenediisocyanate.
 8. The adhesive of claim 7 further comprising a urethane catalyst.
 9. A method of making a two part structural polyurethane adhesive useful for adhering a first unprimed fiber reinforced polyester substrate to a second unprimed substrate comprisinga) preparing a prepolymer component by reacting a polyol and excess aromatic polyisocyanate whereby said prepared prepolymer has 3 to 15 percent free isocyanate groups, b) admixing an aliphatic polyisocyanate with said prepolymer of step a, forming the first part of said two part adhesive, and c) separately combining polyfunctional polyether polyol and diamine forming the second part of said two part adhesive.
 10. The method of claim 9 wherein said aliphatic polyisocyanate has an aliphatic carbon alpha to said isocyanate group wherein said alpha carbons are --CH₂ R, --CHRR' or --CRR R", where R, R' and R" are independently substituted or unsubstituted aromatic groups or substituted or unsubstituted aliphatic groups of six to forty carbon atoms.
 11. The method of claim 10 wherein said aliphatic isocyanate has a molecular weight from 120 to
 700. 12. The method of claim 11 wherein said aliphatic isocyanate is selected from the group consisting of isophorone diisocyanate, bis- (4-isocyanatocyclohexyl) methane, m-xylylenediisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, m-tetramethylxylene diisocyanate, dimethyl-p-isopropenyl benzyl isocyanate, trimethyl hexamethylene diisocyanate, 2-isocyanatoethyl 2, 6 diisocyanatohexanoate, hexamethylene diisocyanate an mixtures thereof.
 13. The method of claim 12 wherein said primerless adhesive comprises about 100 weight parts combined prepolymer and curative and from 0.5 to 6.0 weight parts aliphatic isocyanate.
 14. The method of claim 13 wherein said primerless adhesive comprises from 50 to 85 weight parts prepolymer, from 0.5 to 6.0 weight parts aliphatic isocyanate, and the balance curative to make 100 parts.
 15. The method of claim 14 wherein said primerless adhesive comprises about 80 parts prepolymer, about 20 parts curative and from 0.5 to 4.0 parts m-xylylenediisocyanate.
 16. The method of claim 15 further comprising a urethane catalyst. 